One in every 20 worldwide victims of banking "malware" is now an Australian, according to monitoring data released by software security firm Trend Micro.
Only the US and Brazil have more victims, accounting for about one in three and one in five of the total, respectively.
"Australia is proportionately getting a lot of banking malware," said Jonathan Oliver, the company's software architecture director for Australia and New Zealand.
"It's causing concern among many people in the IT security," he told AAP.
The country is a prime target because it is an "early adopter" of technology, meaning a high proportion of the population use the internet and online banking, he said.
And, unlike their European counterparts, Australian banks have been slow to introduce additional layers of security, like two-step verification with a mobile phone.
Malware is often downloaded when people open a fraudulent email attachment. It can then monitor browsing habits and steal usernames and passwords.
Trend Micro's global security systems detected a surge in the number of distinct infections in the first half of the year - from 130,000 between January and March to 146,000 between April and June.
The report found a particularly large jump in June, with 71,000 distinct infections compared with 39,000 in May.
The spread is being driven partially by the wider availability of malware, which cybercriminals can now buy cheaply and in two-for-one packages.
The spread of malware means emails are now less likely to con readers into directly divulging their passwords, but will instead plant software that secretly monitors browsing.
Oliver said people should always accept updates to software such as Java, which are designed to combat emerging malware threats.
